Macbook AC power hiss

My Macbook (not pro) makes an annoying hiss/buzz noise when it's on AC power. It's not deafening by any means but it's non-trivial when using it in a quiet room. I gather this is a common fault but I can't find any solution. Ideas? Are Apple likely to replace it if I complain?

My Macbook (not pro) makes an annoying hiss/buzz noise when it's on AC power. It's not deafening by any means but it's non-trivial when using it in a quiet room. I gather this is a common fault but I can't find any solution. Ideas? Are Apple likely to replace it if I complain?

Thanks,

Mark

It's possibly something to do with the display inverter, or the CPU buzzing. Mine actually hisses more on battery than it does on AC - but does hiss whilst charging (even with the second core turned off).